In the face of accelerating climate change, the transition towards a nonnuclear renewable energy system represents a key political challenge, which can be aggravated by the increasing energy supply uncertainty created by the shift away from fossil fuels. In this article, we conduct a comparison of the expansion of renewable energy sources in Austria, Belgium, and Germany at the level of their subnational units (federal states), thereby covering three economically very important central European federal European Union members. We consider potentially influential factors in a fuzzy-set qualitative comparative analysis: In addition to state-specific socioeconomic and geographical characteristics, political factors, such as parties in government, and specific energy-related policy instruments are included in the analysis. We find that a high potential for renewable electricity expansion in combination with low financial prosperity is most likely to lead to a successful expansion of renewable electricity ...